A new quantity called the target reproduction number is defined to measure control strategies for infectious diseases with multiple host types such as waterborne, vector-borne and zoonotic diseases. The target reproduction number includes as a special case and extends the type reproduction number to allow disease control strategies that target contacts between host types. Relations involving closed walks and cycles in a weighted digraph are used to derive new expressions for target reproduction numbers. Several disease models in the literature and new cholera models are used to illustrate the applications of the target reproduction number.